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Sun Q.,China University of Mining and Technology | Xue X.,Shanxi Railway Institute | Zhu S.,China University of Mining and Technology
Guti Lixue Xuebao/Acta Mechanica Solida Sinica | Year: 2013

The phenomena caused by rock brittle fracture can be divided into two types. One is related to the changes in physical-mechanical parameters and structural characteristics, which can be described as the rock fracture, the decrease of bearing capacity and modulus, the increase of permeability and deformation, and the sudden change of wave velocity and resistance. The other one is related to the release of energy and change of physical parameters, which is shown by the increase of acoustic emission (AE), electromagnetic emission and infrared radiation. Experiment and theoretical results show that the stress ratio between critical point of brittle failure and its peaking point falls within a range of 70% to 80%. This research shows that the comprehensive information source can be adopted to identify the critical point of brittle fracture. Source


Wang W.,Ningbo University | Huang Y.,Ningbo University | Su R.,Shanxi Railway Institute | Wang X.,Ningbo University
Applied Mechanics and Materials | Year: 2011

In order to study fracture mechanics of high strength steel with the moderate thickness, fracture tests were performed on 10 plates with elliptical hole fabricated from high strength steel Q345 with the thickness of 16mm. The effect of the notch sharpness (the ratio of the length of short axis to that of long axis of elliptic hole, b/a) and the notch depth (the ratio of the length of long axis of the elliptic hole to the width of plate, 2a/w) on fracture model of high strength steel was examined. Test results show that the first crack initiates at the notch edge. The fracture ductility is lower for the specimens with the sharper notch (a smaller ratio b/a) and the deeper notch (a larger ratio 2a/w), and the point of crack load lies in hardening phase of load-displacement curve. The fracture ductility is higher for the specimens with the obtuse notch (a larger ratio b/a), and the point of fracture load lies in necking phase of load-displacement curve. The ultimate strength of notched plates is independent of the notch sharpness (b/a) and the notch depth (2a/w). © (2011) Trans Tech Publications. Source


Wang W.-Z.,Ningbo University | Wang W.-Z.,Lanzhou University of Technology | Jiang L.-Y.,Ningbo University | Sun R.-Q.,Lanzhou University of Technology | And 2 more authors.
Advanced Materials Research | Year: 2011

In order to study fracture mechanics of high strength steel with the moderate thickness, fracture tests were performed on 10 elliptical notched plates with the thickness of 16mm fabricated from high strength steel Q345. The effect of notch sharpness (the ratio of the length of short axis to that of long axis of elliptic notch, b/a) and notch depth (the ratio of the length of long axis of elliptic notch to the width of plate, a/w) on fracture model of high strength steel was examined. Test results show that the first crack initiates at the notch edge. The fracture ductility is low for the specimens with the sharper notch (a smaller ratio b/a), and the point of crack load lies in hardening phase of load-displacement curve. The fracture ductility is high for the specimens with the obtuse notch (a bigger ratio b/a), and the point of fracture load lies in necking phase of load-displacement curve. There is no qualitative relationship of fracture ductility and the notch depth (a/w). The ultimate strength of notched plates is independent of the notch sharpness (b/a) and notch depth (a/w). © (2011) Trans Tech Publications. Source


Zhu H.-Y.,Shanxi Railway Institute | Li H.-B.,State Key Laboratory of Shield Machine and Boring Technology | Zhang H.-P.,State Key Laboratory of Shield Machine and Boring Technology | Ren Y.-Y.,State Key Laboratory of Shield Machine and Boring Technology
Zhendong yu Chongji/Journal of Vibration and Shock | Year: 2016

TBM tools have to be replaced frequently because of wear. There is a lack of an effective method to evaluate the tool condition in underground construction. The acoustic emission technology is applied to detect the health condition of the TBM tool. Single or multiple acoustic emission features were used to estimate the wear trend according to the acoustic emission signals from a TBM mode at different levels of wear. An improved CRITIC method to evaluate hob wear was put up. The disc cutter wear test showed that the improved CRITIC method is more sensitive to the tool wear levels. The new method is more efficient to evaluate and predict tool wear, and it provides guidance for repairing and maintaining of the cutting tool. © 2016, Editorial Office of Journal of Vibration and Shock. All right reserved. Source


Li H.,University of Jinan | Qin L.,University of Jinan | Feng Y.,Shanxi Railway Institute | Hu L.,University of Jinan | Zhou C.,University of Jinan
Journal of Magnetism and Magnetic Materials | Year: 2015

A kind of double-layered self-assembly sodium alpha-olefin sulfonate (AOS) capped Fe3O4 magnetic nanoparticles (Fe3O4-AOS-MN) with highly water-solubility was prepared by a wet co-precipitation method with a pH of 4.8. The resulting Fe3O4-AOS-MN could be dispersed into water to form stable magnetic fluid without other treatments. The result of X-ray diffraction (XRD) indicated that the Fe3O4-AOS-MN maintained original crystalline structure and exhibited a diameter of about 7.5 nm. The iron oxide phase of nanoparticles determined by Raman spectroscopy is Fe3O4. Transmission electron microscopy (TEM) analysis confirmed that the Fe3O4-AOS-MN with spherical morphology were uniformly dispersed in water. FT-IR spectroscopy (FT-IR) and thermo-gravimetric analysis (TGA) verified the successful preparation of Fe3O4-AOS-MN capped with double-layered self-assembled AOS. The corresponding capacities of monolayer chemical absorption and the second-layer self-assembly absorption were respectively 4.07 and 14.71 wt% of Fe3O4-MN, which were much lower than those of other surfactants. Vibrating sample magnetometer (VSM) test result showed Fe3O4-AOS-MN possessed superparamagnetic behavior with the saturation magnetization value of about 44.45 emu/g. The blocking temperature TB of Fe3O4-AOS-MN capped with double-layered AOS is 170 K. © 2015 Elsevier B.V. All rights reserved. Source

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